a. Field of the Invention
This invention relates generally to medical instruments, and more specifically, to electrode catheter devices with one or more indifferent electrodes for direct current tissue therapies.
b. Background Art
Catheters are typically flexible, tubular devices that are widely used by physicians performing medical procedures to gain access into interior regions of the body. Catheters may be used to apply energy (e.g., radiofrequency (RF) energy) to form lesions in tissue at a desired location. It is well known that benefits can be gained if the depth and location of these lesions can be controlled, which changes the electrical properties of the tissue. For example, lesions can be formed at specific locations in cardiac tissue to lessen or eliminate undesirable atrial fibrillation or other arrhythmias.
Several difficulties can be encountered, however, when attempting to form lesions at specific locations using some existing electrodes. One such difficulty encountered with existing catheters relates to how to control the energy using conventional techniques. Typically, the physician forms lesions in the tissue based on personal experience using the catheter. Such experience only comes with time, and can be quickly lost if the physician does not use the catheter on a regular basis. In addition, when forming lesions in a heart, the beating of the heart further complicates matters, making it difficult to maintain sufficient contact pressure between the catheter and the tissue for a sufficient length of time to form a desired lesion. If the contact between the catheter and the tissue cannot be properly maintained, a quality lesion is unlikely to be created. In addition, using RF may result in uneven lesion formation. For example, more RF energy may be emitted near the RF electrode and “tail-off” farther away from the RF electrode. Likewise, the RF energy emitted by adjacent electrodes may overlap, or alternatively, not fully cover the tissue area between the RF electrodes, if the electrodes are not properly spaced.